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1

Which two types of molecular interactions are most important in stabilising the structure of the DNA double helix?

Hydrogen bonds an hydrophobic interactions

2

RNA structure:

-RNA consists of unbranches chains of nucleotides

- the phosphodiester links in RNA join the 5’ position of one nucleotide with the 3’ position of the adjacent nucleotide

- the bases in RNA are uracil, adenine, guanine, cytosine

- RNA is single stranded = relative amounts of purines and pyrimidines are not fixed

3

Restriction endonucleases =

Cut the phosphodiester bonds between adjacent nucleotides in DNA

4

Quinolones =

Inhibit DNA gyrase

5

Actinomycin D =

Inhibits transcription by binding to DNA

6

Cycloheximide =

Inhibits protein synthesis in eukaryotes

7

Chloramphenicol =

Binds to the prokaryotic 70s ribosome particle

8

Which amino acid is sulphur present in =

Cysteine and methionine

= only these form disulphide bonds

9

Km =

Michaelis constant = the substrate concentration which gives 50% of the maximal rate

10

In a lineweaver-burk plot :

Intersection on Y axis = 1/Vmax

Intersection on x axis = -1/Km

Gradient = Km/Vmax

11

Which amino acid is present at the active site of pancreatic ribonuclease and is involved in the catalysis of RNA hydrolysis ?

Histidine + lysine

12

What are the substrates of DNA polymerase enzymes ?

Template DNA
Primer with 3’-OH
Deoxynucleotide trisphosphates
Mg2+

13

What are the products of DNA polymerase enzymes?

Pyrophosphate
The growing strand is one nucleotide longer

14

How does DNA polymerase 1 differ from 3?

DNA polymerase 3 =
Faster
More processive
Lacks 5’ > 3’ exonuclease activity
Has multiple subunits

15

Differences between primase and DNA polymerase enzymes?

- primase makes RNA and doesn’t need primer
- DNA polymerase makes DNA and requires a primer

16

What role does 3’-OH on the ribose play in the polymerase reaction ?

Nucleophilic attack of the a-phosphorous of the incoming dNTP

17

Give two examples of posttranscriptional modification of RNA in bacteria -

Base modification in tRNA/rRNA
Ribose methylation in tRNA/rRNA

18

Which type of bacteria
RNA is not subject to processing ?

mRNA

19

Which enzyme synthesises mRNAs in eukaryotes?

RNA polymerase 2

20

What posttranscriptional modification occur at the ends of eukaryotic mRNAs ?

Capping at 5’ end
Tail addition at 3’ end
Cleavage prior to addition of tail

- happens in the nucleus

21

Splicing =

Excision of introns sequences from the mRNA primary transcript and joining of the exons

22

Low Km =

Higher affinity of an enzyme for its substrate

23

Competitive inhibitor effectors on…

Km increase
Vmax unchanged

24

Non competitive inhibitor effects on…

Km unchanged
Vmax decrease

25

Collagen can be found…

Skin, bones, cartilage, tendons, teeth